I'm not sure if the issues with the Hyperflow ever got documented here so I thought I would mention that the first batch of Hyperflows have defective cartridges. If you have a defective cartridge you can call MSR at 1-800-531-9531 to get it replaced. I just recently got mine replaced and the filter now works as advertised. Pumps easy and fast, and the backflush works properly. For more info check this out: http://www.whiteblaze.net/forum/showthread.php?t=45798&highlight=hyperflow.